Efficient production line for aerosol cans

ABSTRACT

A production line with processing stations processing products with a production speed in products per unit time, the production line comprising a temporarily discontinuously operating processing station; a production line section connected upstream of the temporarily discontinuously operating processing station; a production line section connected downstream from the temporarily discontinuously operating processing station; a first product buffer arranged between the upstream production line section and the temporarily discontinuously operating processing station; and a second product buffer arranged between the temporarily discontinuously operating processing station and the downstream production line section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC §119 to German PatentApplication No. 10 2011 080 769.1 filed on Aug. 10, 2012, whichapplication is hereby incorporated by reference.

TECHNICAL FIELD

The invention relates to a production line with processing stationswhich process products per unit time with a production speed, whereinthe production line includes a processing station operatingdiscontinuously from time to time, a production line section arrangedupstream of the processing station and a production line sectionarranged downstream of the processing station.

BACKGROUND OF THE INVENTION

Production lines of the type recited supra are known in the art and arebeing used for example when producing and/or processing containers likeaerosol cans, beverage cans or tubes.

Typical production speeds of production lines of this type are between50 and 2500 containers per minute (subsequently designated as cpm),wherein production speeds of greater than 500 cpm are typically usedduring mass production of beverage cans, production speeds of less than100 cpm are used in the production of special containers like aluminumtubes. Production lines for producing aerosol cans are configured for aproduction speed between 100 cpm and 500 cpm, in particular between 150cpm and 250 cpm.

The containers to be produced are typically combined in so-calledbatches, wherein a batch defines a number of containers which areprocessed by a discontinuously operating processing station between tworetrofits of the processing station. In aerosol can production, thebatch size is typically 10000 to 1000000 containers.

For the duration of a retrofit wherein the retrofit is for example adécor change of a decoration station, besides the processing stationitself standing still that needs to be retrofitted, also the upstream ordownstream production line section of the processing station standsstill.

In order to compensate the productivity reduction caused by a standstillof this type, a processing station that operates discontinuously fromtime to time and the upstream or downstream production line section ofthe processing station are configured for a production speed which istypically significantly higher than a production speed of a productionline without retrofit requirement.

SUMMARY OF THE INVENTION

The invention is based on the finding that the cost for a productionline is disproportionally high in the prior art, since the entireproduction line is configured for a higher production speed.

It is the object of the present invention to provide a production linewith a processing station that operates discontinuously from time totime, wherein the production line achieves high productivity with lowestpossible complexity. This object is achieved by a production line inthat a first product buffer is arranged between the upstream productionline section and the processing station that temporarily operates in adiscontinuous manner and a second product buffer is provided between theprocessing station that temporarily operates in a discontinuous mannerand the downstream production line section and the production line isconnected with a control which controls the production line so that thetemporarily discontinuously operating processing station after aproduction interruption of the processing station operates withincreased production speed relative to the upstream and the downstreamproduction line section until the initially filled first product bufferis depleted down to a predetermined amount and/or the initially depletedsecond product buffer is filled to a predetermined amount.

In the production line according to the invention, the upstreamproduction line section and the downstream production line section incase of a production interruption of the temporarily discontinuouslyoperating processing station can continue to produce until the initiallydepleted first product buffer is filled to a predetermined amount and/orthe initially filled second production buffer is depleted to apredetermined amount, so that the upstream production line section andthe downstream production line section can have a lower production speedthan comparable prior art production line sections without theproduction speed of the entire production line being lower.

The solution according to the invention includes the finding that priorproduction improving measures are directed to increasing productionspeed in itself. It was also found that a higher production speed comeswith a higher scrap rate which in turn causes an effective productivityreduction. A significant quality increase of the products produced isachieved in that the maximum production speed is only increased in oneprocessing station, thus the processing station temporarily operating ina discontinuous manner and the maximum production speeds of theproduction line sections that are connected upstream or downstream arelimited.

Discontinuous manner in this context means that a processing stationoperating in a discontinuous manner temporarily does temporarily notoperate with its actual production speed but that its production istemporarily interrupted, wherein the interruption does not have tocoincide with an abrupt change of the production speed, for examplebetween standstill (for a production interruption) and increasedproduction speed. A discontinuous operating mode rather means that atransition of the production speed from standstill to another productionspeed can be provided without speed leaps.

The solution according to the invention can be supplemented withadditional advantageous embodiments. Some of the embodiments aresubsequently described.

In a particularly preferred embodiment, the temporarily discontinuouslyoperating processing station is a deco station for decorating a productwith a respectively replaceable decoration. Replacing the decorationrequires retrofit time which causes a respective production interruptionof the deco station. The production buffers have a buffer capacity whichare respectively adjusted to the production speed of the upstreamproduction line section or the downstream production line section sothat a filling time used with this production speed for filling thefirst product buffer and/or an emptying time used for emptying thesecond product buffer is greater than or equal to the retrofit time.

In order to facilitate an optimum loading of the production line, thecontrol can control the upstream production line section and thedownstream production line section so that the upstream production linesection and the downstream production line section operate with theirmaximum possible production speed as long as the number of products tobe processed in a batch is greater or equal to the product of theemptying time of the first product buffer related to this maximumproduction speed and the maximum possible production speed of theupstream production line section.

As long as the number of the products to be processed in a batch is lessthan the product of the emptying time of the first product bufferrelated to the maximum production speed of the upstream production linesection and the downstream production line section and the maximumpossible production speed of the upstream production line section, thecontrol can cause the upstream production line section and thedownstream production line section to operate with a reduced productionspeed relative to its maximum possible production speed. Thisfacilitates a reliable production in particular for small batch sizes.

In order to be configured in an optimum manner for the requirements ofaerosol can production, the upstream production line section and thedownstream production line section in an advantageous embodiment areconfigured for a maximum production speed of 200 products per minute. Inan alternative embodiment, the temporarily discontinuously operatingprocessing station is configured for a maximum production speed of 250products per minute. In another advantageous embodiment, the upstreamproduction line section and the downstream production line section areconfigured for a maximum production speed of 250 products per minute.

For a particularly advantageous operation of the production line, themaximum production speed of the upstream production line section and ofthe downstream production line section can be higher than 150 productsper minute and lower than 300 products per minute. In order tofacilitate particularly uniform filling and emptying of the productbuffers, the control can control the upstream production line and thedownstream production line so that the production speed of the upstreamproduction line and the production speed of the downstream productionline are identical.

In a particularly advantageous embodiment, the upstream production linesection includes an extrusion press and the downstream production linesection includes a fold over station. Since stations of this type arevery expensive, limiting their maximum production speed is particularlyadvantageous for the cost of the entire production line.

The deco station can include a coating unit, a decoration unit, alacquering unit and the associated drying ovens. In an alternativeembodiment, the temporarily discontinuously operating processing stationis configured as a decoration drying oven.

In another advantageous embodiment, the upstream production line sectionincludes a drawing device and/or a stretching device. The downstreamproduction line section can include a combined drawing-stretchingdevice. In a particularly advantageous embodiment, the drawing device isa “cupper”. The stretching device can be a “body maker”.

The object of the invention is achieved through a method for operating aproduction line, wherein the production line includes a temporarilydiscontinuously operating processing station, a production line sectionconnected upstream of the temporarily discontinuously operatingprocessing station, a production line section connected downstream ofthe temporarily discontinuously operating processing station, a firstproduct buffer arranged between the upstream production line section andthe temporarily discontinuously operating processing station and asecond product buffer arranged between the temporarily discontinuouslyoperating processing station and the downstream production line section.

The method provides that the temporarily discontinuously operatingprocessing station is operated with an increased production speedrelative to the upstream and the downstream production line sectionafter a production interruption of the processing station until theinitially filled first product buffer is emptied to a predeterminedamount and/or the initially emptied second product buffer is filled to apredetermined amount.

The upstream production line section and the downstream production linesection can continue to produce in case of a production interruption ofthe temporarily discontinuously operating processing station until theinitially emptied first product buffer is filled to a predeterminedamount and/or until the initially filled second product buffer isdepleted to a predetermined amount.

In a particularly advantageous embodiment, the method providesretrofitting the temporarily discontinuously operating processingstation, wherein the processing station is a deco station for decoratinga product with a respectively replaceable decoration and theretrofitting means a replacement of the decoration with a retrofit timewhich causes a respective production interruption of the deco station.The production buffers have a buffer capacity which is respectivelyadapted to the production speed of the upstream production line sectionand/or of the downstream production line section so that a filling timethat is used at this production speed for filling the first productbuffer and an emptying time that is used at that production speed foremptying the second product buffer is great than or equal to theretrofit time.

In an advantageous embodiment, the upstream production line section andthe downstream production line section are operated with their maximumproduction speed as long as the number of the products to be processedin a batch is greater than or equal to the product of the emptying timeof the first buffer related to this maximum production speed and themaximum possible production speed of the upstream production linesection.

In a particularly advantageous embodiment, the production speed of theupstream production line section, and of the downstream production linesection, are reduced with respect to their maximum possible productionspeed.

BRIEF DESCRIPTION OF THE DRAWINGS

Subsequently the invention is described with reference to embodimentsillustrated in drawing figures. The different features in the drawingfigures like in the embodiments described supra are randomly combinablewith one another, wherein:

FIG. 1 illustrates a schematic depiction of an exemplary embodiment of aproduction line according to the invention in a stationary productioncondition directly before a retrofit starts;

FIG. 2 illustrates a schematic depiction of an exemplary embodiment ofthe production line of FIG. 1 in a production condition directly after abeginning of a retrofit;

FIG. 3 illustrates a schematic illustration of an exemplary embodimentof the production line according to the invention according to FIG. 1 ina production condition during retrofit;

FIG. 4 illustrates a schematic depiction of an exemplary embodiment ofthe production line according to the invention according to FIG. 1 in aproduction condition directly before an end of the retrofit;

FIG. 5 illustrates a schematic depiction of an exemplary configurationof the production line according to the invention according to FIG. 1 ina production condition directly after the end of the retrofit;

FIG. 6 illustrates a schematic depiction of an exemplary embodiment ofthe production line according to the invention according to FIG. 1 in aproduction condition substantially after the end of the retrofit;

FIG. 7 illustrates a schematic depiction of an exemplary embodiment ofthe production line according to the invention according to FIG. 1 in aproduction condition directly before reaching a stationary productioncondition;

FIG. 8 illustrates an exemplary embodiment of the production lineaccording to the invention according to FIG. 1 in a stationaryproduction condition; and

FIG. 9 is a chart that illustrates the required difference in productionspeeds according to the invention.

DETAILED DESCRIPTION

An assembly line 100 in FIGS. 1 through 8 includes a temporarilydiscontinuously operating processing station 1 with a production speedv1. The temporarily discontinuously operating processing station 1 has aproduction line section 2 connected upstream and a production linesection 3 connected downstream. The production line section 2 operateswith a production speed v2, the production line section 3 operates witha production speed v3.

Between the upstream production line section 2 and the temporarilydiscontinuously operating processing station 1, a first product buffer 4with a buffer level p4 is arranged between the temporarilydiscontinuously operating processing station 1 and the downstreamproduction line section 3 a second product buffer 5 with a buffer levelp5 is arranged. A transfer of the products to be processed from thefirst product buffer 4 to the processing station 1 is provided with atransfer speed v6, a transfer of the process products from theprocessing station 1 to the product buffer 4 is provided with a transferspeed v7. The change of the buffer level p4 per minute is indicated asv4, the change of the buffer level p5 per minute is designated as v5. Apositive prefix of v4 or v5 indicates an increasing buffer level, anegative prefix indicates a decreasing buffer level.

With reference to the configuration of the production lines 100described in FIGS. 1 through 6, a retrofit time T of 30 minutes isdefined. The upstream production line section 2 and the downstreamproduction line section 3 are configured for a maximum production speedof 200 cpm, the temporarily discontinuously operating processing stationis configured for a maximum production speed of 250 cpm. The upstreamproduction line section 2 and the downstream production line section 3are continuously operated with their maximum production speeds of 200cpm.

During a retrofit of the temporarily discontinuously operatingprocessing station 1, the upstream production line section 2 and thedownstream production line section 3 continue to operate with theirmaximum production speed of 200 cpm, thus they process a number of 6,000containers respectively during the retrofit time of 30 minutes (200cpm×30 min.). In order to maintain a continuous production, therefore, abuffer size of 6,000 containers is required for the product buffers 4and 5. After the retrofit is completed, the product buffer 4 has grownto 6,000 containers, the product buffer 5 is emptied.

The number of 6,000 containers corresponds to the amount to which theproduct buffer 4 or the product buffer 5 are filled, the number of 0containers corresponds to the predetermined amount to which the productbuffer 4 or the product buffer 5 are depleted. The buffer capacitycorresponds to 6,000 containers.

For the retrofit required for the next batch, the buffer level p5 has tobe reduced to its original amount of p5=6,000, the buffer level p4 hasto be reduced to its original amount of p4=20. Since the temporarilydiscontinuously operating processing station 1 is configured for amaximum production speed of 250 cpm and thus exceeds the productionspeed of the upstream production line section 2 or the downstreamproduction line section 3 by 3 to 50 cpm, this yields a time frame of120 minutes (6,000/(250 cpm-50 cpm)) for completely loading the productbuffer 5 or unloading the product buffer 4.

In the time frame of 120 minutes, the upstream production line section 2and the downstream production line section 3 of 24,000 containers (120minutes×200 cpm) is run through. This number of 24,000 containers thusrepresents a maximum batch size B up to which a continuous operation ofthe upstream production line section 2 and the downstream productionline section 3 is feasible.

These definitions refer to the instant embodiment and do not represent ageneral limitation. Furthermore, it is clear to a person skilled in theart that the defined values are not maintained mathematically exact inproduction reality, they rather are subject to normal technicalvariations and other production technique considerations.

FIG. 1 illustrates the production line in a stationary productioncondition, the stationary mode. The entire production line 100 operateswith a uniform production speed of 200 cpm (v1=v2=v3=v6=v7=200 cpm). Theproduct buffer 4 is in empty condition (p4=0), whereas 6,000 containersare included by the second product buffer 5 (p5=6,000).

FIGS. 2 through 4 illustrate the production line during retrofit, theretrofit mode. During this time, the temporarily discontinuouslyoperating processing station 1 stands still (v1=0 cpm), a transfer ofproducts from the first product buffer 4 to the processing station 1does not occur and a transfer of products from the processing station 1to the product buffer 4, this means the transfer speed v7 or v6 are 0cpm. The upstream production line section 2 and the downstreamproduction line section 3 operate with a production speed of 200 cpm,wherein these production line sections process a number of 6,000containers respectively (200 cpm×30 minutes) during the retrofit timeperiod. This number determines the buffer requirement for maintaining acontinuous production.

When the retrofit mode starts (FIG. 2), the buffer level p4 of theproduct buffer 4 increases at 200 cpm, the buffer level p5 of theproduct buffer 5 decreases with 200 cpm. After a retrofit time of 5minutes, the product buffer 4 includes 1,000 containers (p4=1,000), theproduct buffer 5 has a level of 5,000 containers (p5=5,000).

During the retrofit mode (FIG. 3) after 15 minutes, the product buffer 4includes 3,000 containers (p4=3,000), the product buffer 5 also has alevel of 3,000 containers (p5=3,000).

Directly before an end of the retrofit mode (FIG. 4), after 28 minutes,the product buffer 4 includes 5,600 containers (p4=5,600), the productbuffer 5 has a level of 400 containers (p5=400).

At an end of the retrofit mode after 30 minutes, the product buffer 4includes 6,000 containers (p4=6,000), the product buffer 5 is empty(p5=0).

FIGS. 5 through 7 illustrate the production line during filling theproduct buffer 4, the refill mode. In refill mode which comes directlyafter the retrofit mode, the temporarily discontinuously operatingprocessing station 1 operates with an increased production speed (v1=250cpm). A transfer of products from the first product buffer 4 to theprocessing station 1 and a transfer of product from the processingstation 1 to the product buffer 4 is accordingly provided respectivelywith an increased transfer speed, this means the transfer speeds v7 orv6 are 250 cpm respectively. The upstream production line section 2 andthe downstream production line section 3 continue to operate with theproduction speed of 200 cpm. For the product buffer, this yields a netof −50 cpm (v2−v6), this means the buffer level p4 decreases, the bufferlevel p5 increases by 50 cpm (v7−v3), this means the buffer level p4increases. Since the buffer level p5 has to be reduced to its originalamount of p5=6,000, this yields a duration of the filling mode of 120minutes (6,000/50 cpm).

Five minutes after the refill mode begins (FIG. 5), the product buffer 5includes 250 containers (p5=250), the product buffer 4 has a level of5,750 containers (p4=5,750).

During the refill mode (FIG. 6), this means 60 minutes after the refillmode begins, the product buffer 5 includes 3,000 containers (p5=3,000),the product buffer 4 also includes a level of 3,000 containers(p4=3,000).

Directly before an end of the refill mode (FIG. 7), this means 110minutes after the refill mode begins, the product buffer 5 includes5,500 containers (p5=5,500), the product buffer 4 has a level of 500containers (p4=500).

When the refill mode ends after 120 minutes, the product buffer 5 iscompletely filled (p5=6,000), the product buffer 4 does not include anymore containers (p4=0).

FIG. 8 in turn illustrates a production line 100 in a stationaryproduction condition which follows directly after the refill modedescribed with reference to FIGS. 5 through 7. The entire productionline 100 operates with uniform production speeds of 200 cpm(v1=v2=v3=v6=v7=200 cpm). The product buffer 4 is in empty condition(p4=0), whereas 6,000 containers are included in the second productbuffer 5 (p5=6,000).

The subsequent tables summarize parameters for the precedingembodiments.

Reference Numeral/Production Stationary Mode Retrofit Mode Refill ModeCondition (FIG. 1, FIG. 8) (FIG. 2-FIG. 4) (FIG. 5-FIG. 7) p4 (c =Container) 0    0-6000 6000-0 v4 (cpm) 0 200 −50 p5 (c = Container) 6006000-0    0-6000 v5 (cpm) 0 −200 50 v6 (cpm) 200 0 250 v7 (cpm) 200 0250 v1 (cpm) 200 0 250 v2 (cpm) 200 200 200 v3 (cpm) 200 200 200

In the embodiment described supra, 24,000 containers (120 minutes×200cpm) are respectively processed by the upstream production line section2 and the downstream production line section 3 within 120 minutes whichcorresponds to the time period for completely loading the product buffer5 or unloading the product buffer 4. This means that the entireproduction line processes 24,000 containers—one batch—in these 120minutes. The number of 24,000 containers which represents a typicalbatch size during aerosol production by the same token represents aminimum batch size up to which a continuous operation of the upstreamproduction line section 2 and the downstream production line section 3is possible at its maximum production speed of 200 cpm.

The design parameters used for the preceding configuration can bedetermined in a general manner so that they go beyond the particularembodiment.

Reciting another embodiment, depending on the batch size to be processedand the retrofit time, the upstream production line section 2 and thedownstream production line section 3, for example, can have a maximumproduction speed of 150 cpm and the temporarily discontinuouslyoperating processing station 1 can have an increased production speed of200 cpm (150/200 operating mode). Additional operating modes are forexample 150/180, 250/300 or 250/350.

FIG. 9 illustrates the required difference in production speeds, thismeans the amount by which the production speed of the temporarilydiscontinuously operating processing station after a productioninterruption of this processing station has to exceed the productionspeed of the upstream and downstream production line sections in orderto facilitate a continuous production for the entire production line asa function of the batch size and the respective retrofit time.

FIG. 9 is based on the subsequent general formula according to which thefirst and the second product buffer have the same buffer capacity andthe temporarily upstream connected production line section and thedownstream production line section have the same production speed:

Difference of production speeds=retrofit time×(production speed of theproduction line section)²/batch size, wherein batch size=emptying timeof product buffer*production speed of the upstream production linesection.

Emptying time of product buffer=buffer capacity of productbuffer/(increased production speed of the temporarily discontinuouslyoperating processing station−production speed of the upstream productionline section).

Buffer capacity of the product buffer=retrofit time×production speed ofupstream production line section.

1. A production line with processing stations processing products with aproduction speed in products per unit time, the production linecomprising: a temporarily discontinuously operating processing station;a production line section connected upstream of the temporarilydiscontinuously operating processing station; a production line sectionconnected downstream from the temporarily discontinuously operatingprocessing station; a first product buffer arranged between the upstreamproduction line section and the temporarily discontinuously operatingprocessing station; and a second product buffer arranged between thetemporarily discontinuously operating processing station and thedownstream production line section, wherein the production line isconnected with a control controlling the production line, wherein thetemporarily discontinuously operating processing station operates withan increased production speed that is increased relative to the upstreamproduction line section and the downstream production line section aftera production interruption of the temporarily discontinuously operatingprocessing station until the initially filled first product buffer isemptied to a predetermined level and/or the initially emptied secondproduct buffer is filled to a predetermined level, and wherein theupstream production line section and the downstream production linesection can continue to produce in case of a production interruption ofthe temporarily discontinuously operating processing station until theinitially emptied first product buffer is filled to a predeterminedlevel and/or the initially filled second product buffer is emptied to apredetermined level.
 2. The production line according to claim 1,wherein the temporarily discontinuously operating processing station isa deco station for decorating a product with a respectively replaceabledecoration, wherein replacing the decoration requires a retrofit timewhich causes a respective production interruption of the deco station,and wherein the production buffers have a buffer capacity which isrespectively adjusted to the production speed of the respective upstreamproduction line section and the respective downstream production linesection, so that a filling time provided at this production speed forfilling the first product buffer and/or an emptying time provided foremptying the second product buffer is greater or equal to the retrofittime.
 3. The production line according to claim 1, wherein the controlcontrols the upstream production line section and the downstreamproduction line section so that the upstream production line section andthe downstream production line section operate at their maximum possibleproduction speeds if the number of products to be processed in a batchis greater or equal to the product of the emptying time of the firstproduct buffer related to this maximum production speed and the maximumpossible production speed of the upstream production line section, andif this condition does not apply, the upstream production line sectionand the downstream production line section operate with a productionspeed that is reduced relative to their maximum possible productionspeed.
 4. The production line according to claim 1, wherein the upstreamproduction line section and the downstream production line section areconfigured for a maximum production speed of 200 products per minute. 5.The production line according to claim 1, wherein the upstreamproduction line section and the downstream production line section areconfigured for a maximum production speed of 250 products per minute. 6.The production line according to claim 1, wherein the control controlsthe upstream production line section and the downstream production linesection so that the production speed of the upstream production linesection and the production speed of the downstream production linesection are equal.
 7. The production line according to claim 1, whereinthe upstream production line section includes an extrusion press and thedownstream production line section includes a folding station.
 8. Theproduction line according to claim 1, wherein the upstream productionline section includes a drawing device and/or a stretching device or acombined drawing—stretching device.
 9. A method for operating aproduction line including a temporarily discontinuously operatingprocessing station, a production line section connected upstream of thetemporarily discontinuously operating processing station, a productionline section connected downstream from the temporarily discontinuouslyoperating processing station, a first product buffer arranged betweenthe upstream production line section and the temporarily discontinuouslyoperating processing station, and a second product buffer arrangedbetween the temporarily discontinuously operating processing station andthe downstream production line section, comprising: operating thetemporarily discontinuously operating processing station with anincreased production speed that is increased relative to the upstreamproduction line section and the downstream production line section aftera production interruption of the temporarily discontinuously operatingprocessing station until the initially filled first product buffer isemptied to a predetermined level and/or the initially emptied secondproduct buffer is filled to a predetermined level, wherein the upstreamproduction line section and the downstream production line section cancontinue to produce in case of a production interruption of thetemporarily discontinuously operating processing station until theinitially emptied first product buffer is filled to a predeterminedlevel and/or the initially filled second product buffer is emptied to apredetermined level.
 10. The method according to claim 9, furthercomprising: retrofitting the temporarily discontinuously operatingprocessing station, wherein the temporarily discontinuously operatingprocessing station is a deco station for decorating a product with arespectively replaceable decoration, wherein replacing the decorationrequires a retrofit time which causes a respective productioninterruption of the deco station, and wherein the production buffershave a buffer capacity which is respectively adjusted to the productionspeed of the respective upstream production line section and therespective downstream production line section, so that a filling timeprovided at this production speed for filling the first product bufferand/or an emptying time provided for emptying the second product bufferis greater or equal to the retrofit time.
 11. The method according toclaim 9, further comprising: operating the upstream production linesection and the downstream production line section at their maximumpossible production speeds if the number of products to be processed ina batch is greater or equal to the product of the emptying time of thefirst product buffer related to this maximum production speed and themaximum possible production speed of the upstream production linesection, and if this condition does not apply, reducing the productionspeed of the upstream production line section and the downstreamproduction line section relative to their maximum possible productionspeed.